The substance of the Whole is passive and malleable, and the reason directing this substance has no cause in itself to do wrong, as there is no wrong in it: nothing it creates is wrongly made, nothing harmed by it. All things have their beginning and their end in accordance with it.
If you are doing your proper duty let it not matter to you whether you are cold or warm, whether you are sleepy or well-slept, whether men speak badly or well of you, even whether you are on the point of death or doing something else: because even this, the act in which we die, is one of the acts of life, and so here too it suffices to 'make the best move you can'.
Look within: do not allow the special quality or worth of any thing to pass you by.
All that exists will soon change. Either it will be turned into vapour, if all matter is a unity, or it will be scattered in atoms.
The governing reason knows its own disposition, what it creates, and what is the material for its creation.
I typically don't commentate on multiple passages, but in this case, the first five passages in Book 6 seem to be interconnected. Marcus begins by noting that the "reason directing" the universe does nothing wrong. The reason guiding the universe simply exists. Things within the universe begin and then they end.
Then he shifts focus to himself as an entity within that universe. He counsels himself to always do his duty come cold or heat, whether tired or rested, when he's been maligned or praised or even at the point of death. We always have a choice to do our duty; so always do it. In a summary, he's counseling himself what he should do - his actions.
In the third passage, he continues to counsel himself, this time on his attitude and judgments. He should embrace all that is of special worth and quality (temperance, courage, justice, wisdom - in a word: virtue).
In the fourth, he returns the idea of change and the reason directing it. Whether a unity (god) or random atoms, we have to embrace things either way.
And lastly he returns to where he started Book 6 - the governing reason. It just is - it exists and we have to accept whatever that governing reason creates along with the material it uses.
(see also Citadel p. 166)